The invention pertains to a steering device for a motor vehicle which contains an inductive module for the contactless transmission of electric energy and data between the motor vehicle and the steering wheel, for measuring the rotational angle of the steering wheel and for generating torque between the motor vehicle and the steering wheel, with the inductive module containing a stator that is connected to the motor vehicle in a torsionally rigid fashion and a rotor that is connected to the steering wheel in a torsionally rigid fashion.
DE 197 36 346 C1 discloses a device for transmitting electric energy between the motor vehicle side and the steering wheel side of a motor vehicle which utilizes a resolver-based rotation sensor. The corresponding method, in particular, indicates that this device is also able to simultaneously determine the rotational angle of the steering wheel and to transmit data between the steering wheel side and the motor vehicle side.
However, this publication does not discuss the possibility of using such a device for generating torque between the steering wheel and the motor vehicle.
The generation of such torque is, for example, known in conventional steering mechanisms for motor vehicles in order to boost the steering forces exerted by the driver of the motor vehicle or in so-called xe2x80x9csteer-by-wirexe2x80x9d steering devices in order to generate counter steering moments for realizing a haptic feedback for the driver of the motor vehicle.
For example, DE 198 22 170 A1 discloses a power steering device for generating a steering boost in reaction to a steering control signal. In this case, electromotor means are used for generating the boosting forces, with the electric motor arranged within the region of the steering gear inevitably resulting in a decentralized arrangement of the components.
EP 04 47 626 B1 discloses an actuator for a cybernetic steering system, in which electric motors arranged axially referred to a steering spindle are provided in order to generate torques for moving a steering pinion of the power steering system as well as for simulating a steering moment in the steering wheel.
The utilization of the same technical principle for the transmission of energy and data into the steering wheel as well as the simultaneous measurement of the steering angle is neither disclosed in this application nor considered apparent as particularly evident from the chosen arrangement distant from the steering wheel.
Based on the previously cited state of the art, the invention aims to develop a steering device for a motor vehicle, in which the tasks of energy and data transmission between the motor vehicle and the steering wheel, steering angle measurement and torque generation are realized with one compact component that exclusively utilizes inductive principles. It should be possible to realize such a unit which has a very small space requirement with the least number of components possible and in a particularly inexpensive fashion.
This objective is attained due to the fact that the steering device is based on an inductive module that contains a stator that is connected to the motor vehicle in a torsionally rigid fashion and a rotor that is connected to the steering wheel in a torsionally rigid fashion, as well as a resolver-based rotation sensor for the contactless transmission of electric energy and data between the motor vehicle and the steering wheel and for measuring the rotational angle of the steering wheel, and an annular rotary-field motor for generating torque between the motor vehicle and the steering wheel, with the stator and the rotor containing coils that cooperate with one another in such a way that an inductive coupling exists between the coils on the stator side which are provided for realizing the rotation sensor function and the rotary-field motor function and the respectively assigned coils on the rotor side.
In the steering device according to the invention, at least three coils are respectively provided on the stator side and on the rotor side on the periphery of a circle around the axis of rotation of the steering wheel in order to realize the rotation sensor function and the rotary-field motor function, with the respective coils being equidistantly spaced apart.
In order to prevent gaps in the overlap between the coils on the rotor side and the coils on the stator side, the number and/or arrangement of the coils on the stator side, in particular, differ(s) from the number and/or arrangement of the respectively assigned coils on the rotor side.
According to one embodiment, the coils are arranged concentric to one another in a plane that lies perpendicular to the rotational axis of the steering wheel. In another embodiment, the coils are arranged in planes that are axially offset relative to one another, with the axes of the coils being aligned radial or parallel referred to the rotational axis of the steering wheel in both aforementioned embodiments.
A particularly effective inductive coupling between the stator and the rotor can be achieved if they contain flux guide elements that are essentially realized in an annular fashion and have an E-shaped radial cross section in the region of the coils and a U-shaped radial cross section in the region between the coils, with the flux guide elements consisting, in particular, of a thermoplastic plastic material that is filled with a low-retentivity material
The flux guide elements are preferably realized by means of a thermoplastic extrusion coating of the coils with plastic that is filled with a low-retentivity material.
An even more compact unit that, due to the additional elimination of components, is also particularly inexpensive can be achieved if the same coils are provided on the stator side in order to realize the rotation sensor function and the rotary-field motor function.
The space requirement and the costs can be additionally reduced with an embodiment in which the same coils are provided on the stator side and on the rotor side in order to realize the rotation sensor function and the rotary-field motor function. In this case, individual coils or groups of coils of the stator and the rotor can be controlled in a chronologically offset fashion.
The invention also proposes that the steering wheel be directly connected to a steering gear that influences the position of the motor vehicle wheels with the aid of a steering rod assembly via a steering spindle. In this case, the torques generated by the rotary-field motor are used for boosting the steering forces exerted by the driver of the motor vehicle. Alternatively, the angular position of the steering wheel which is determined by the rotation sensor is used for influencing the position of the motor vehicle wheels by means of electromotor driven means, with the torques generated by the rotary-field motor being used as counter steering moments for realizing a haptic feedback for the driver of the motor vehicle.
Additional advantages of the invention are disclosed as well as the following description of the embodiments that are illustrated in the figures and elucidate the design and function of the device according to the invention.